This invention relates to sample cups used to hold samples for analysis by X-ray fluorescence ("XRF") spectrometers. In particular, this invention relates to an insert for such sample cups, which insert aids in the elimination of bubbles from liquid samples.
Sample cups, typically, are made from a suitable material such as polyethylene, and have a cylindrical body that can be open from one end or both ends. A respective collar, generally made from the same material as the body, preferably is provided for closing each open end with a preferably transparent thin film. The collar locks into a suitable detent on the body. The sample cup with one open end is used by adding the sample to the body, covering the open end with the thin film, and fastening the thin film by snapping the collar over the film and into the detent on the body. This captures the thin film, creating a taut, preferably transparent window. If the cup has two open ends, one end is sealed with the film and collar prior to the introduction of the sample and sealing of the second end. The sample cup is then placed in the XRF spectrometer and analyzed. Depending on the type of instrument, the X-ray source directs a beam, preferably into the center of the sample cup, either from above or from below.
In such known sample cups, air bubbles may be trapped under the film during sealing of the cup. When the sample cup is used with instruments in which the beam is directed into the sample from above, if such bubbles rest near the center of the cup, they may interfere with the X-ray beam, thereby spoiling the analysis. In addition, regardless of the type of sample cup, even if the sample is initially bubble-free, bubbles may form as a result of outgassing from the sample. In one known attempt to deal with the problem of air bubbles, sample cups were constructed with special ports for the introduction of syringes for the purpose of removing the air bubbles. This method of air bubble removal, however, was time-consuming, difficult to reproduce from sample to sample, messy, caused the cell to become unbalanced due to the uneven distribution of the weight caused by the hole and seal, and risked contamination of the sample.
In view of the foregoing, it would be desirable to provide a sample cup insert that permits the user to substantially eliminate the air bubbles from within the portion of the sample to be analyzed.
It would further be desirable to provide a sample cup insert that permits the user to substantially eliminate the air bubbles from within the portion of the sample to be analyzed quickly and easily.
It would be still further desirable to provide a sample cup insert that permits the user to eliminate the air bubbles from the portion of the sample to be analyzed after the sample is sealed inside the sample cup, so that substantially no additional air bubbles can enter the portion of the sample to be analyzed.
It would yet further be desirable to provide a sample cup insert that is adapted for use in known sample cups, thereby allowing the user to use the invention with sample cups that can alternatively be used for powder and paste samples as well.